Condensate corrosion prevention methods

As many emissions involve chlorinated compounds, corrosion is a major problem in many control methods. The corrosion of columns and surface condensers can be prevented or reduced by the correct material selection. However, corrosion remains a constant threat to the interior of incinerators. Additional pollution control equipment such as scrubbers may also be required to remove acidic compounds from treated gases before discharging into the atmosphere. 

Fig. 9.6 Method of preventing corrosion by premature condensation of acidic vapours. pH measured continuously at point X automatically controls flow of sodium hydroxide...

If any of these components are absent, the metal will not corrode. For example, sachets of silica gel are put into display cabinets to prevent corrosion by stopping an electrolyte from condensing on the metal surfaces. Museums, nowadays, use more refined methods of humidity control for cabinets. 

Transport of gasoline and other refined products in steel pipelines may result in corrosion products that can create a product contamination problem. Internal corrosion of the pipeline can also have an adverse effect on pipeline capacity. Corrosion results from condensation of a water film on the pipe wall plus dissolved air or SRB in the product. Corrosion control is commonly achieved by adding a corrosion inhibitor. Evaluation of inhibitor performance can be done using NACE Test Method for Antirust Properties of Cargoes in Petroleum Product Pipeline (TM0172). This test method is a modification of ASTM D 665, Test Method for Rust-Preventing Characteristics of Inhibited Mineral Oil in the Presence of Water. 

The condensed water droplets are entrapped and removed. The physical drying methods prevent water contact with downstream equipment like compressors, pipes, activated carbon beds, and other parts of the process, thus avoiding the problem of corrosion. 

The following methods can be adopted to prevent corrosion in the condensate system ... 

The prevention of deposit formation is important in boilers as the deposits (scales, sludges, corrosion products, etc.) act as insulators, causing a loss of heat transfer. The thicker the deposit, the greater the driving force required to penetrate the barrier and higher the temperature of the tubes. There are several methods to control deposits and some important methods are summarized below. The majority of the corrosion products that deposit in the boiler originate in the condensate system, for instance ... 

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